Diffusion NMR study of complex formation in membrane-associated peptides.
Eur Biophys J
; 42(5): 405-14, 2013 May.
Article
em En
| MEDLINE
| ID: mdl-23389300
ABSTRACT
Pulsed-field-gradient nuclear magnetic resonance (PFG-NMR) is used to obtain the true hydrodynamic size of complexes of peptides with sodium dodecyl sulfate SDS micelles. The peptide used in this study is a 19-residue antimicrobial peptide, GAD-2. Two smaller dipeptides, alanine-glycine (Ala-Gly) and tyrosine-leucine (Tyr-Leu), are used for comparison. We use PFG-NMR to simultaneously measure diffusion coefficients of both peptide and surfactant. These two inputs, as a function of SDS concentration, are then fit to a simple two species model that neglects hydrodynamic interactions between complexes. From this we obtain the fraction of free SDS, and the hydrodynamic size of complexes in a GAD-2-SDS system as a function of SDS concentration. These results are compared to those for smaller dipeptides and for peptide-free solutions. At low SDS concentrations ([SDS] ≤ 25 mM), the results self-consistently point to a GAD-2-SDS complex of fixed hydrodynamic size R = (5.5 ± 0.3) nm. At intermediate SDS concentrations (25 mM < [SDS] < 60 mM), the apparent size of a GAD-2-SDS complex shows almost a factor of two increase without a significant change in surfactant-to-peptide ratio within a complex, most likely implying an increase in the number of peptides in a complex. For peptide-free solutions, the self-diffusion coefficients of SDS with and without buffer are significantly different at low SDS concentrations but merge above [SDS] = 60 mM. We find that in order to obtain unambiguous information about the hydrodynamic size of a peptide-surfactant complex from diffusion measurements, experiments must be carried out at or below [SDS] = 25 mM.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Peptídeos
/
Membrana Celular
Tipo de estudo:
Prognostic_studies
/
Risk_factors_studies
Idioma:
En
Ano de publicação:
2013
Tipo de documento:
Article